Integrated circuit including vertical capacitors

ABSTRACT

In some examples, an integrated circuit comprises a first plate, a second plate, and a dielectric layer disposed between the first and second plates, the first and second plates and the dielectric layer forming a vertical capacitor, wherein the first and second plates and the dielectric layer of the vertical capacitor are disposed on an isolation region of the integrated circuit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/977,712 filed May 11, 2018, which is incorporated herein by referencein its entirety.

BACKGROUND

A non-volatile-memory (NVM) bitcell is an electronic element that isconfigured to store information. The electrical state (e.g., thresholdvoltage) of a bitcell can be used to define a logic level, such as alogic low level (meaning digital low or 0) or a logic high level(meaning digital high or 1). This defined logic level may sometimes bereferred to as information (or a bit) stored in the bitcell.

SUMMARY

In accordance with at least one example, an integrated circuit comprisesa first plate, a second plate, and a dielectric layer disposed betweenthe first and second plates, the first and second plates and thedielectric layer forming a vertical capacitor, wherein the first andsecond plates and the dielectric layer of the vertical capacitor aredisposed on an isolation region of the integrated circuit.

In accordance with another example, an integrated circuit comprises afloating gate flash bitcell comprising at least a control gate layer, aword line gate layer, and a dielectric layer. The integrated circuitalso comprises a vertical capacitor disposed on a shallow trenchisolation (STI) region, the vertical capacitor comprising the controlgate layer, the word line gate layer, and the dielectric layer, thedielectric layer positioned between the control gate layer and the wordline gate layer.

In accordance with yet another example, a method of fabricating anintegrated circuit having at least one vertical capacitor on a shallowtrench isolation (STI) region on a substrate, comprises depositing afirst dielectric layer on the STI region; depositing a first polysiliconlayer on the first dielectric layer; patterning the first polysiliconlayer to form a first plate of the vertical capacitor having a sidewall;depositing a second dielectric layer such that the second dielectriclayer contacts the sidewall; and depositing a second polysilicon layersuch that the second polysilicon layer contacts the second dielectriclayer, the second polysilicon layer forms a second plate of the verticalcapacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various examples, reference will now bemade to the accompanying drawings in which:

FIG. 1(a) depicts a portion of an illustrative layout of a floating gateflash bitcell memory array, in accordance with various examples.

FIG. 1(b) depicts a side-view cross-section of a pair of illustrativebitcells, in accordance with various examples.

FIG. 1(c) depicts an illustrative layout of an array of verticalcapacitors, in accordance with various examples.

FIG. 1(d) depicts a side-view cross-section of illustrative verticalcapacitors, in accordance with various examples.

FIG. 2 depicts an illustrative method performed to fabricate verticalcapacitors, in accordance with various examples.

FIGS. 3(a)-3(g) depict the fabrication of an illustrative bitcell, inaccordance with various examples.

FIGS. 4(a)-4(g) depict the fabrication of at least one verticalcapacitor, in accordance with various examples.

DETAILED DESCRIPTION

Flash memory is a non-volatile storage medium that may store informationin an array of bitcells. This stored information (or “bit”) can beelectrically erased, programmed, and read. In some cases, an array offloating-gate transistor bitcells may be used in flash memory. Afloating-gate transistor bitcell resembles a standardmetal-oxide-field-effect-transistor (MOSFET), except that thefloating-gate transistor bitcell includes multiple gates, e.g., controlgate and floating gate. As noted above, an electrical state of a bitcellcan be used to define a logic level, which can be referred to as a bitstored in the bitcell. This may be performed using changes in thresholdvoltages of the bitcells. The threshold voltage of a floating-gate typetransistor bitcell may change because of the presence or absence oftrapped charge in its floating gate, which further alters the thresholdvoltage (relative to the old threshold voltage) of the floating-gatetransistor bitcell. The threshold voltage (or the electrical state ofthe floating-gate transistor bitcell) when electrons are trapped in thefloating-gate type transistor bitcell can be characterized to as adigital low or “0” stored as a bit in the bitcell. On the contrary, theelectrical state when electrons are depleted in the floating gate can bereferred to as digital high or “1” stored as a bit in the bitcell.

As described above, the characterization (e.g., digital high or low) ofa bit stored in a floating-gate bitcell depends on the presence orabsence of a charge in the floating gate. In some cases, a charge isstored/depleted in a floating gate by applying a voltage potential(e.g., greater than or equal to 10V) at the control gate of thefloating-gate transistor bitcell. In some cases, a charge pump circuitis used to apply the voltage potential. A typical charge pump circuitboosts the input charge to provide voltages higher than the voltagesupplied to it. In some cases, a charge pump circuit is capacitor-based,and typically, a capacitor-based charge pump circuit employs capacitorssuch as a metal-over-semiconductor (MOS).

A MOS capacitor typically includes a layer of metal (e.g., metalcontact), a layer of insulating material (e.g., silicon dioxide), and alayer of semiconductor material (e.g., silicon). These layers aretypically laterally fabricated, and the fabrication design of thesecapacitors results in a parasitic capacitance generated between thesubstrate (e.g. p-type silicon substrate) and the plates of thecapacitors (e.g., nwell), which interferes with the capacitance of theMOS capacitor and degrades its performance. To avoid the parasiticcapacitance interference, planar poly-to-poly capacitors ormetal-to-poly capacitors are employed in the charge pumps. However, thefabrication of such capacitors requires extra masks, which increases theoverall manufacturing cost. Therefore, an alternative design ofcapacitors that may be used in charge pump circuits and that mitigatesthe concerns mentioned above is desired.

Accordingly, at least some of the examples described in this disclosureare directed towards systems and methods for fabricating verticalcapacitors that may be used in floating gate flash bitcell technology.In at least some examples, vertical capacitors disclosed herein arefabricated on the same die as the floating-gate flash bitcells, withoutusing additional masks. The vertical capacitors described in thisdisclosure are positioned in isolation regions, such as the shallowtrench isolation (STI) regions. The disposition of vertical capacitorson the STI regions prevents interference from the above-mentionedparasitic capacitance (e.g., nwell to p-substrate). In at least someexamples, the vertical capacitors utilize the word line gate layers andthe control gate layers of the flash bitcells as their capacitor plates.In at least some examples, the control gate layers and the word linegate layers are separated by a dielectric layer, which may comprise amulti-layer structure.

Referring now to FIG. 1(a), a portion of an illustrative layout 100 of afloating gate flash bitcell memory array (or floating gate bitcells) isshown in accordance with various examples. The layout 100 depicts atleast some of the layers that form an array of floating gate bitcells.The layout 100 includes bit line (BL) layers 106, 108, 110, 112, 114,and 116, and a source line (SL) layer 124. The layout 100 also includesword line (WL) gate layers 118, 122, erase gate (EG) layer 120, andcontrol gate (CG) layers 102, 104. The region occupied by the BL layers106, 108, 110, 112, 114, and 116 is sometimes referred to as an activeregion. The layout 100 also depicts at least some of the layers thatform the vertical capacitors to be utilized in the charge pump circuits(e.g., WL gate layers 118, 122, and CG layers 102, 104). This disclosureis not limited to a floating gate bitcell array including theaforementioned gate layers. The description of vertical capacitors belowis valid for other types of floating gate bitcells, including floatinggate bitcells that do not employ an erase gate layer.

FIG. 1(a) also illustrates a coordinate system 1, where the X-axis andthe Y-axis of the coordinate system 1 each lie in the page of thedrawing, and the Z-axis lies away from (outwards) the page of thedrawing. For example, from a layout 100 perspective (as shown in FIG.1(a)), one or more bitcells are positioned on line 50 aligned with theY-axis; however, from a fabrication perspective (as shown in FIG. 1(b)),a side-view of the cross-section of one or more bitcells may be observedin the Y-Z plane along the line 50.

The layout 100, at least in part, is used as a layout (or blueprint) tofabricate an array of floating gate bitcells and an array of verticalcapacitors that are implemented along with a CMOS logic array (notexpressly depicted). In some examples, the layout 100 may be used tofabricate an array of bitcells that is implemented as a standalonememory device (e.g., implemented on its own semiconductor die, enclosedwithin its own chip package, etc.). In some examples, the layout 100 maybe used to fabricate an array of bitcells that is implemented in anintegrated circuit (IC) (e.g., implemented on a semiconductor die thatincludes additional circuit(s)).

Referring now to FIG. 1(b), a side-view cross-section of a pair ofillustrative bitcells 70, 80 may be observed in the Y-Z plane along theline 50 (FIG. 1(a)) through the bit line 112. Other bitcells may beobserved in the Y-Z plane along other bit lines 106, 108, 110, 114, and116 that are present on the Y-axis.

The bitcells 70 and 80 are substantially similar in structure. Thebitcell 70 includes a bit line layer 112 that is disposed in a substrate126. The bitcell 70 also includes the word line (WL) gate layer 118, thecontrol gate layer 102, the floating gate layer 132, and the erase gatelayer 120 (that is also shared by the bitcell 80). A dielectric layer142 is located over the control gate layer 102. The bitcell 70 furtherincludes dielectric layers 138, 140. These dielectric layers arefabricated to provide isolation between the word line gate layer 118,the control gate layer 102, the floating gate layer 132, and the erasegate 120. In some examples, the substrate 126 may include silicon. Insuch examples, the dielectric layer 140 may include silicon dioxide, andthe dielectric layer 138 may include silicon nitride. The bitcell 70also includes a dielectric layer 111 that acts as the floating gatedielectric and provides isolation between the floating gate 132 and thesubstrate 126. The bitcell 70 forms a WL transistor that includes the WLgate layer 118 (analogous to a gate of a MOSFET), the bit line layer 112(analogous to a drain of a MOSFET), and the source line layer 124(analogous to a source of a MOSFET). The bitcell 70 also includes animplant layer 128 that is disposed below the word line gate layer 118 inthe substrate 126. In some examples, the implant layer 128 may be usedto alter the threshold voltage of the WL transistor. In some examples,the substrate 126 also includes an additional implant layer, such as,the anti-punch through layer 136 that is formed by implanting dopants(e.g., boron) in the substrate 126. Although the bitcell 70 (or an arrayof such bitcells) depicted in FIG. 1(b) includes the erase gate layer120, the control gate layer 102, the word line gate layer 118, and thefloating gate layer 132, the description in this disclosure is notlimited to a floating gate bitcell 70 including the aforementioned gatelayers. This description is valid for a floating gate bitcell array,where each of the floating gate bitcells includes the word line gatelayer 118, the control gate layer 102, and the floating gate layer 132.

Similar to the bitcell 70, the bitcell 80 includes the bit line 112, thesource line layer 124, the erase gate layer 120, the floating gate layer134, the control gate layer 104, and the word line gate layer 122. Adielectric layer 144 is located over the control gate layer 104, and animplant layer 130 is located under the word line gate layer 122. Thebitcell 80 also includes dielectric layers 146, 148, which isolate theword line gate layer 122, the control gate layer 104, the floating gatelayer 134, and the erase gate 120 from each other. The bitcell 80 alsoincludes a dielectric layer 111 that acts as the floating gate 134dielectric and provides isolation between the floating gate 132 and thesubstrate 126. In some examples, the substrate 126 may include silicon.In such examples, the dielectric layer 146 may include silicon dioxide,and the dielectric layer 148 may include silicon nitride. In someexamples, the word line gate layers 118, 122, and the control gatelayers 102, 104 comprise polysilicon.

In some examples, bitcells 70, 80 may be fabricated in an integratedcircuit (IC) (e.g., implemented on a semiconductor die that includesadditional circuit(s)).

As noted above, vertical capacitors form using the word line gate layersand control gate layers on the same die as the array of floating gatebitcells. Unlike the bitcells 70, 80 that are fabricated on thesubstrate 126, the vertical capacitors—to prevent parasitic capacitanceinterference—are fabricated on an isolation region (e.g., STI region).Although this disclosure generally describes vertical capacitors on asingle STI region, in some examples, multiple vertical capacitors aredistributed among multiple isolation regions (e.g., STI regions).

FIG. 1(c) depicts an illustrative layout 160 of an array of verticalcapacitors that are formed using the control gate layers 167, 169, 171,. . . , 237 and the word line gate layers 166, 168, 170, . . . , 236 ofbitcells (not expressly shown) disposed in the same die as the verticalcapacitors. The layout 160 includes the contact layer 162 that coupleswith each of the control gate layers 167, 169, 171, . . . , 237. Thelayout 160 also includes the contact layer 164 that couples with each ofthe word line gate layers 166, 168, 170, . . . , 236. In some examples,the word line gate layers 166, 168, 170, . . . , 236 and the controlgate layers 167, 169, 171, . . . , 237 comprise polysilicon.

In some examples, the layout 160, along with the layout 100, may be usedto fabricate an array of vertical capacitors and bitcells that areimplemented in an integrated circuit (IC) (e.g., implemented on asemiconductor die that includes additional circuit(s)).

Referring now to FIG. 1(d), a side-view cross-section of verticalcapacitors disposed along a portion of line 165 (FIG. 1(c)) is depicted.FIG. 1(d) depicts vertical capacitors 251-260 that are disposed on theSTI region 250, which is positioned on the substrate 126. The capacitorsdepicted in FIG. 1(d) comprise the word line gate layers 166, 168, 170,172, 174, and 176 and the control gate layers 167, 169, 171, 173, and175. For example, the word line gate layer 166 acts as one of the platesand the control gate layer 167 acts as the other plate of the verticalcapacitor 251. In some examples, a dielectric layer 261 is disposedbetween the word line gate layer 166 and the control gate layer 167. Insome examples, this dielectric layer 261 may comprise a tri-layerstructure. In some examples, this tri-layer structure includes twodielectric layers 271 that are oxide layers and a dielectric layer 272that is a nitride layer. In examples where the substrate comprisessilicon, the dielectric layers 271 comprise silicon dioxide, and thedielectric layer 272 comprises silicon nitride. Other materials may alsobe used.

Similar to the vertical capacitor 251 formed between the word line gate166 and the control gate 167, a vertical capacitor 252 forms between thecontrol gate layer 167 and the word line gate layer 168, with thedielectric layer 262 disposed between them. Similar to the verticalcapacitor 251, the vertical capacitor 252 is also disposed on the STIregion 250. In some examples, the dielectric layer 262 comprises atri-layer structure. In some examples, this tri-layer structure includestwo dielectric layers 296 that are oxide layers and a dielectric layer297 that is a nitride layer. In examples where the substrate comprisessilicon, the dielectric layers 296 comprise silicon dioxide, and thedielectric layer 297 comprises silicon nitride. Similar to the verticalcapacitors 251, 252, vertical capacitors 253-260 form between word linegate layers 168, 170, 172, 174, and 176 and the control gate layers 169,171, 173, and 175 on the STI region 250, with each vertical capacitor253-260 including a dielectric layer, which, in turn, may comprise atri-layer structure.

Referring now to FIG. 2, an illustrative method 300 may be performed tofabricate the vertical capacitors that are positioned on the STI region.The method 300 is now described in tandem with the illustrativefabrication flow diagrams depicted in FIGS. 3(a)-3(g) and FIGS.4(a)-4(g). FIGS. 3(a)-3(g) depict the fabrication of an illustrativebitcell including at least a control gate layer and a word line gatelayer, and FIGS. 4(a)-4(g) depict the fabrication of at least onevertical capacitor that employs the control gate layer and the word linegate layer of the above-referenced bitcell to form its parallel plates.

The steps depicted in FIGS. 3(a)-3(g) may be observed along the line 50(FIG. 1(a)), and the steps depicted in FIGS. 4(a)-4(g) may be observedalong the line 165 (FIG. 1(c)).

For simplicity's sake, the fabrication steps depicted in FIGS. 3(a)-3(g)are of a single bitcell, and the steps depicted in FIGS. 4(a)-4(g) areof at least one vertical capacitor that is formed using the control gatelayer and the word line gate layer of the bitcell. However, in otherexamples, the description may be adapted for the fabrication of aplurality of bitcells and vertical capacitors.

The method 300 begins with obtaining the substrate 126 that comprisesSTI regions (step 310), such as the STI region 401 (FIG. 4(a)), whichcomprises silicon dioxide. STI regions are created early during thesemiconductor device fabrication process, before other electronicelements (e.g., transistors, bitcells) are formed. In some examples, thefabrication of STI regions involves etching a pattern of trenches (notexpressly shown in FIGS. 3(a)-3(g) and 4(a)-4(g)) in the substrate, suchas the substrate 126. Further steps in the fabrication of STI regionsinclude depositing one or more dielectric materials (e.g., silicondioxide) to fill the trenches, and then eliminating the excessdielectric material using planarization techniques (e.g.,chemical-mechanical planarization).

In some examples, following the step 310, additional steps (notexpressly included in the method 300) may be performed. The additionalsteps may include depositing a floating dielectric layer 405 and afloating gate layer 410 to form a portion of the bitcell (FIG. 3(a),FIG. 3(b), respectively). The deposition of the gate layer 410 can beobserved in FIG. 4(b); however, the deposition of the dielectric layer405 is masked to contain it to the fabrication of the bitcell. In someexamples, the dielectric layer 405 may be fabricated such that thedielectric layer 405 is disposed on the STI region 410 (not expresslydepicted in FIG. 4(b)). In some examples, the floating gate layer 410comprises polysilicon. In some examples, the aforementioned depositionsteps may be performed using chemical vapor deposition.

In some examples, from a vertical capacitor's perspective, the method300 may also include removing the floating gate layer 410 from the STIregion 401 (FIG. 4(c)). The floating gate layer 410 may be removed usingmasking techniques and the dry/wet etching technique such that the gatelayer 410 is removed from the STI region 401 (FIG. 4(c)) and not fromthe dielectric layer 405 of FIG. 3(c). In some examples, thechemical-mechanical polishing technique may be used to remove thefloating gate layer 410 from STI region 401.

Following the removal of the floating gate layer 410 from the STI region401, the method 300 may proceed to step 320, which may includedepositing the dielectric layer 413. From the vertical capacitor'sperspective, the dielectric layer 413 is deposited on the STI region 401(FIG. 4(c)), and from bitcell's perspective, the dielectric layer 413 isdeposited on the floating gate layer 410 (FIG. 3(c)). In some examples,the dielectric layer 413 may comprise a tri-layer structure. In someexamples, this tri-layer structure includes two dielectric layers 412,416 that comprise silicon dioxide and a dielectric layer 414 thatcomprises silicon nitride. In some examples, the step 320 may alsoinclude implanting dopants (e.g., boron) in the substrate 126 to form ananti-punch through layer 136 (FIG. 3(c)).

The method 300 then moves to step 330, which includes depositing acontrol gate layer 420 on the dielectric layer 413. The control gatelayer 420 can be observed from the perspective of both the verticalcapacitor (FIG. 4(c)) and the bitcell (FIG. 3(c)). In some examples, thestep 330 may also include depositing a dielectric layer 430 on thecontrol gate layer 420. Again, the dielectric layer 430 can be observedfrom both the vertical capacitor's (FIG. 4(c)) and bitcell's (FIG. 3(c))perspectives. In some examples, the deposition of both the control gatelayer 420 and the dielectric layer 430 may be performed using chemicalvapor deposition. In some examples, the control gate layer 420 includespolysilicon, and the dielectric layer 430 includes silicon nitride.

The method 300 may then move to the step 340 that includes patterningthe control gate layer 420 (FIGS. 3(d) and 4(d)). The patterning may beperformed using photo lithography and dry plasma etching. From thevertical capacitor's perspective, the control gate 420, or at least someportion of the control gate layer 420, following the step 340, forms afirst plate of the vertical capacitor. As noted above, for simplicity'ssake, the method 300, FIGS. 3(a)-3(g), and FIGS. 4(a)-4(g) describe theformation of a single bitcell and at least one vertical capacitor. Inother examples, the patterning may be performed such that a plurality ofbitcells and vertical capacitors may form. FIG. 4(d) shows the sidewalls2, 3 of the patterned control gate layer 420.

The method 300 may proceed to step 350, which includes depositingdielectric layers 417 on the sidewalls 2, 3 of the control gate layer420 (FIG. 4(e)). The deposition of dielectric layers 417 can also beobserved in FIG. 3(e). Although FIG. 4(e) depicts the dielectric layers417 abutting the control gate layer 420 and the dielectric layer 430(e.g., the deposition of the dielectric layers 417 may extend from thetop of the dielectric layer 416 to the top of the dielectric layer 430),in some examples, the dielectric layers 417 abut only the control gatelayer 420. In some examples, following the deposition of the dielectriclayers 417, a portion of the floating gate layer 410 may beetched/removed, which is further followed by implantation of dopants(such as boron) in the substrate 126. In some examples, the dielectriclayers 417 assume a tri-layer structure, which includes the dielectriclayers 421, 422, 423. In some examples, the dielectric layers 421, 423comprise silicon dioxide, and the dielectric layer 422 comprises siliconnitride.

The method 300 may then proceed to step 360, which includes depositing apolysilicon layer 424 such that the polysilicon layer 424 is disposed ontop of the dielectric layer 416, the dielectric layers 421, 422, 423,and the dielectric layer 430 (FIGS. 3(f), 3(g), 4(f), and 4(g)). Thestep 360 may also include etching a portion of the polysilicon layer 424to form two separate polysilicon layers 415 and 418 (FIGS. 3(g) and4(g)), which are referred to as word line gate layer and erase gatelayer, respectively.

In the foregoing discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . .” The abovediscussion is meant to be illustrative of the principles and variousembodiments of the present disclosure. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

What is claimed is:
 1. An integrated circuit comprising: a first plate;a second plate; and a dielectric layer disposed between the first andsecond plates, the first and second plates and the dielectric layerforming a vertical capacitor, wherein the first and second plates andthe dielectric layer of the vertical capacitor are disposed on anisolation region of the integrated circuit.
 2. The integrated circuit ofclaim 1 further comprising a second vertical capacitor, comprising: thesecond plate; a third plate; and a second dielectric layer disposedbetween the second and third plates on the isolation region.
 3. Theintegrated circuit of claim 1, wherein the integrated circuit furthercomprises a flash bitcell that includes at least the first plate and thesecond plate.
 4. The integrated circuit of claim 1, wherein thedielectric layer includes a first silicon dioxide layer, a secondsilicon dioxide layer, and a silicon nitride layer.
 5. The integratedcircuit of claim 1, wherein the isolation region is disposed on asilicon substrate.
 6. The integrated circuit of claim 1, wherein theisolation region includes shallow trench isolation (STI) region.
 7. Theintegrated circuit of claim 1, wherein the isolation region includessilicon dioxide.
 8. An integrated circuit, comprising: a floating gateflash bitcell comprising at least a control gate layer, a word line gatelayer, and a dielectric layer; and a vertical capacitor disposed on ashallow trench isolation (STI) region, the vertical capacitor comprisingthe control gate layer, the word line gate layer, and the dielectriclayer, the dielectric layer positioned between the control gate layerand the word line gate layer.
 9. The integrated circuit of claim 8,wherein the control gate layer and the word line gate layer includepolysilicon.
 10. The integrated circuit of claim 8, wherein the STIregion includes silicon dioxide.
 11. The integrated circuit of claim 8,wherein the STI region is disposed on a silicon substrate.
 12. Theintegrated circuit of claim 8 further comprising a floating gate layer,the dielectric layer positioned between the control gate layer and thefloating gate layer.
 13. The integrated circuit of claim 8, wherein thedielectric layer comprises at least one silicon dioxide layer.
 14. Theintegrated circuit of claim 8, wherein the dielectric layer comprises afirst silicon dioxide layer, a second silicon dioxide layer, and asilicon nitride layer.
 15. An integrated circuit, comprising: a firstdielectric layer over a semiconductor substrate; a first conductive linelocated on the first dielectric layer and a second dielectric layerlocated over the first conductive line, the first conductive line andthe second dielectric layer each having a corresponding first sidewall;a third dielectric layer on the first sidewalls of the first conductiveline and the second dielectric layer; and a second conductive linelocated over the first dielectric layer and contacting the thirddielectric layer.
 16. The integrated circuit of claim 15, wherein thefirst dielectric layer comprises a first silicon dioxide layer, a secondsilicon dioxide layer, and a silicon nitride layer between the first andsecond silicon dioxide layers.
 17. The integrated circuit of claim 15,wherein the third dielectric layer comprises a first silicon dioxidelayer, a second silicon dioxide layer, and a silicon nitride layerbetween the first and second silicon dioxide layers.
 18. The integratedcircuit of claim 15, wherein the first dielectric layer is located overa shallow trench isolation region that includes silicon dioxide.
 19. Theintegrated circuit of claim 15, wherein the first conductive line andthe second dialectic layer each have a second sidewall opposite therespective first sidewalls, and further comprising: a fourth dielectriclayer on the second sidewalls and third conductive line; and a secondconductive line located over the first dielectric layer and contactingthe fourth dielectric layer.
 20. The integrated circuit of claim 15,wherein the second dielectric layer comprises SiN.
 21. The integratedcircuit of claim 15, wherein the first dielectric layer comprises afirst silicon dioxide layer, a second silicon dioxide layer, and asilicon nitride layer between the first and second silicon dioxidelayers.